Rolling boil & temperature ranges

[finny]

I'm looking for a little clarification on when I should be going for a rolling boil and when I should be keeping an eye on temperature. I tried search but all the key words I used bring up almost every thread.

Basically I've done about 15 or so extract batches and I'm looking to move to all grain. First dozen batches I just fired up the burner on hi went till a rolling boil and let it be, never checked a temp, never had a problem. The last few extract batches I bought a thermometer and got in my head regarding temps and notices I had a lot less boil off.

Last night I tried my first all grain (BIAB). Wheat beer, shooting for a 2.75 g batch with about 5lbs of grains roughly 50/50 2 row and wheat. Calculators on here came up with 4.29g for starting boil for a 2.75g batch. All said and done I ended closer to 3.75 g batch. No where near the boil off I should have had. OG came in around 1. 040 rather than the 1.052 the recipe anticipated. I'm thinking majority can be attributed to final volume.

Thinking back I never had a rolling boil. Searching on here say rolling boil is 212f. Strike/Mash temps all list 150f-170f. Odds are i'm in my own head and over thinking something obvious, but what am I doing wrong?

Cliff notes I'm just looking for advice on when I should bring to a rolling boil and when I should be keeping an eye on the thermometer????

 

[jethro55]

As far as boil - when things are at boiling temperature, temperature does not increase by adding more heat when constant pressure is maintained. The added heat input manifests in the energy it takes to convert liquid to vapor. More burner heat, more vapor, more boil off. Not more temperature. A rolling boil does the job of mixing and keeping sediment from scorching.

There really is no need to measure boiling temperature, and there is no way to control it if pressure is not contained. Not sure if that is your question.

So if you were at 212 and not a rolling boil, there would be less boil off.

 

[mvcorliss]

If it is boiling, rolling, violently, or just a little, it is at 212f assuming you are somewhat near sea level. The differences is not a higher or lower temp but a change in how fast the temperature gradient in the pot moves. As you boil, the water at the bottom of the pot reaches 212f first because it is closest to the heat source. Because heat rises, that hot water will rise to the top of the pot where it will cool somewhat and then be replaced at the top by warmer water from the bottom. This rolling action is what you want, to keep the temperature more or less even and to keep the hops moving which (for some reason ;-) ) is important for isomerization. However, the movement does not have to be violent, just enough to move the water and cause bubbling at the surface, not just tiny bubbles up the side of the pot which is a simmer.
So, go ahead and crank up the propane when you start heating the water to get up to a boil. Then you can back off on the heat until you are maintaining a good, but not splashing, violent boil. Doing so will not only save propane but also reduce the amount of boil off.
Keep in mind that once you do a couple of batches you will know what YOUR boil off rate is for YOUR system. Anything written into a recipe is only what the recipe's writer's system gets.
Long winded ... Did I answer your question? 😄

 

[mvcorliss]

Damn I've got to type faster! Jethro beat me to it! But at least I think we agreed and said pretty much the same thing.

 

[finny]

Indirectly I think my question is answered. I just need read rather than think and get some input to clear my head.

Basically I should only be concerned about the thermometer during the mash? Once that is complete, I can essentially put the thermometer away and just bring it to a boil and let it be for the time of then boil. I was carrying my mash temp ranges into my boil and essentially never boiling and therefore not getting the anticipated boil off. I knew I was over thinking something.

 

[Demus]

Indirectly I think my question is answered. I just need read rather than think and get some input to clear my head.

Basically I should only be concerned about the thermometer during the mash? Once that is complete, I can essentially put the thermometer away and just bring it to a boil and let it be for the time of then boil. I was carrying my mash temp ranges into my boil and essentially never boiling and therefore not getting the anticipated boil off. I knew I was over thinking something.

Exactly. Thermometer can come back out at knock off to measure the chilling process, but it serves no real purpose on the boil...

 

[finny]

I guess if it wasn't stupid mistakes we'd never learn anything. Now I'm eager to try again and see if I can get it right. Thanks for the replies!

 

[processhead]

These replies really summed it up well.

Once you reach a boil at 212 F., you can increase the heat applied to the kettle as much as you want, but you can't raise the temperature of the boiling wort. It just boils faster and harder. A little counter intuitive, but that's the physics behind it.

That high school physics lesson might have been one of the few that was worth paying attention to.